X Marks the Spot on the Map EarthCache
X Marks the Spot on the Map
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Located in suburban Joburg in the suburb of Observatory. This marks the point that the old Z.A.R. geologists started their geological survey that ended in the first comprehensive geological map of the Witwatersrand.
Only one detailed geological map of the Witwatersrand has been published to date. It was compiled by the Geological Survey of South Africa. It was printed in August 1916 (almost 30 years after gold was discovered) on a scale of 1:60 000 and was called the, “Geological Map of the Witwatersrand Goldfield”. The mapping was undertaken by Dr Edward Thomas Mellor (1868 – 1940) who was Assistant Director of the Geological Survey.
On 10 January 1910, Mellor commenced his mapping on the corner of De Le Rey Street and Schmidt Streets. De Le Rey Street was named after the Boer general – Koos De Le Rey. Schmidt Street was renamed Mons Road in honour of the battle of Mons in Belgium on 23 August 1914. This was the first major battle the British Empire was involved in during the First World War).
The first entry in Mellor’s field notebook reads, “dip hard ferrug. Shale 45°”, and refers to the Water Tower Slate that was visible at the surface (before the street, pavement and houses and other human activities) covered them. Mellor then traversed southwards along De Le Rey Street, recording the presence of Ripple-marker Quartzite on the corner of De Le Rey and Regent Street East and of the Hospital Hill Quartzites dipping at 45°, where De La Rey Street terminated against the old Union Observatory (hence the name of the suburb).
(Acknowledgments: guidebook to Sites of Geological & Mining Interest on the Central Witwatersrand.; Geological Society of South Africa; 1986).
Although much of the underlying geology is not easily visible at this point – a drive around the neighbourhood (especially to nearby Earthcaches in Cyrildene and past the Observatory Golf Course) give a fair idea of what this spot must have looked like almost a century ago.
This Earthcache will ask you to use the information gathered on your trip to the site, and observations of surrounding areas/suburbs, plus any nearby Earthcaches you may have done to qualify for a log.
In order to qualify to log this cache, you need to answer the following questions and s=email the cache owner. Any logs not accompanied by an email will be deleted.
1) Describe the surrounding area – and also make mention of the place where the signpost is located – in your email.
2) Thinking back a century when there was not so much building or tar roads – can you use your observations of the suburbs and surrounding topography (i.e. hills/valleys, sjhape of the landscape etc.) to decide why this a was a good (or bad) place to start a mapping exercise. Not necessarily this exact corner – but this area. Also look at a normal street map of Joburg (imagine how big it would have been in 1910 – and where the industrial/mining activity was occurring in relation to this point too).
3) The cache description refers to the Slate and Quartzite “dipping” at 45° - what is this dipping? Look at ridges and Earthcaches nearby (The Water Tower Slate Earthcache in Cyrildene will give you a great opportunity to see this up close) to assist in your answer.
4) Why do you think geological maps are important – why not stick to topographic or street maps?
5) What is the main difference between a geological map and a street map and a topographical map?
Additional Hints
(Decrypt)
Erzrzore gb fraq lbhe rznvy!